/* AI Engineering from Scratch — connected curriculum hub */
@import url("./lesson.css");

:root {
  --accent-tint: color-mix(in srgb, var(--accent) 7%, var(--card));
  --accent-line: color-mix(in srgb, var(--accent) 38%, var(--line));
}

[hidden] { display: none !important; }
::selection { background: var(--accent); color: var(--paper); }
:focus-visible { outline: 2.5px solid var(--accent); outline-offset: 3px; }
button, input { font: inherit; }
button { color: inherit; }
.sr-only { position: absolute; inline-size: 1px; block-size: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.num-ltr, .lesson-index, .phase-count, .lesson-row-number { direction: ltr; unicode-bidi: isolate; font-variant-numeric: tabular-nums; }

.skip-link { position: fixed; inset-block-start: 12px; inset-inline-start: 12px; z-index: 20; padding: 8px 14px; background: var(--ink); color: var(--paper); font-family: var(--sans); font-size: 13px; transform: translateY(-160%); }
.skip-link:focus { transform: translateY(0); }

.hub-masthead { position: relative; z-index: 2; min-height: 72px; padding: 20px clamp(24px,5vw,64px); border-bottom: 3px solid var(--ink); display: flex; align-items: center; justify-content: space-between; gap: 24px; font-family: var(--sans); }
.hub-brand { color: var(--ink); text-decoration: none; font-size: 14px; font-weight: 700; }
.hub-brand b { color: var(--accent); }
.hub-brand-en { color: var(--ink-soft); font-size: 10px; font-weight: 700; letter-spacing: .16em; }
.hub-nav { display: flex; align-items: center; gap: 18px; font-family: var(--sans); font-size: 11px; font-weight: 700; }
.hub-nav a { color: var(--accent); text-decoration: none; border-bottom: 1px solid var(--accent-line); }
.hub-nav a:hover { color: var(--ink); border-bottom-color: var(--ink); }
.hub-nav span { color: var(--ink-soft); }
.hub-wrap { position: relative; z-index: 1; max-width: 1180px; margin: 0 auto; padding: 0 30px 120px; }

.hub-hero { padding: clamp(64px,9vw,116px) 0 64px; max-width: 860px; }
.hero-kicker, .ui-label { display: block; margin: 0 0 10px; color: var(--accent); font-family: var(--sans); font-size: 11px; font-weight: 700; letter-spacing: .16em; }
.hub-hero h1 { margin: 0; max-width: 800px; font-family: var(--serif-display); font-size: clamp(48px,8vw,88px); font-weight: 900; line-height: 1.02; letter-spacing: -.025em; }
.hero-lead { max-width: 650px; margin: 28px 0 0; color: var(--ink-soft); font-size: clamp(18px,2.2vw,23px); line-height: 1.75; }

.today { display: grid; grid-template-columns: minmax(0,1.65fr) minmax(260px,.75fr); border-block: 3px solid var(--ink); background: var(--card); }
.today-main { padding: clamp(28px,4vw,48px); }
.today-title { margin: 0 0 16px; font-family: var(--serif-display); font-size: clamp(28px,4vw,42px); line-height: 1.25; }
.today-lesson-meta { margin: 0 0 10px; display: flex; align-items: center; gap: 14px; color: var(--ink-soft); font-family: var(--sans); font-size: 12px; }
.lesson-index { color: var(--accent); font-weight: 900; letter-spacing: .08em; }
.today-lesson-title { margin: 0; font-family: var(--serif-display); font-size: clamp(24px,3vw,34px); line-height: 1.35; }
.today-lesson-en { display: block; margin-top: 2px; color: var(--ink-soft); font-family: var(--sans); font-size: 13px; }
.today-actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; }
.primary-action, .secondary-action { min-height: 44px; padding: 9px 20px; border: 1.5px solid var(--ink); border-radius: var(--radius); font-family: var(--sans); font-size: 13px; font-weight: 700; text-decoration: none; cursor: pointer; transition: background .16s ease, color .16s ease; }
.primary-action { background: var(--ink); color: var(--paper); }
.primary-action:hover { background: var(--accent); border-color: var(--accent); }
.secondary-action { background: transparent; }
.secondary-action:hover { background: var(--paper-2); }
.next-note { margin: 24px 0 0; padding-top: 16px; border-top: 1px solid var(--line); color: var(--ink-soft); font-family: var(--sans); font-size: 12px; }
.next-note b { color: var(--ink); }
.availability { padding: clamp(28px,4vw,48px); border-inline-start: 1px solid var(--line); display: flex; flex-direction: column; justify-content: center; }
.availability-count { display: block; font-family: var(--serif-display); font-size: clamp(38px,5vw,60px); line-height: 1; }
.availability-count small { display: block; margin-top: 10px; color: var(--ink-soft); font-family: var(--sans); font-size: 13px; font-weight: 500; }
.readiness-track { height: 5px; margin-top: 24px; overflow: hidden; background: var(--line); }
.readiness-fill { display: block; height: 100%; background: var(--accent); }
.availability-note { margin: 12px 0 0; color: var(--ink-soft); font-family: var(--sans); font-size: 11px; line-height: 1.65; }

.study-loop { margin: 76px 0 108px; padding: 28px 0; border-block: 1px solid var(--line); display: grid; grid-template-columns: minmax(220px,.7fr) minmax(0,1.5fr); gap: 48px; align-items: center; }
.loop-intro h2 { margin: 0; font-family: var(--serif-display); font-size: 28px; line-height: 1.35; }
.loop-steps { margin: 0; padding: 0; list-style: none; display: grid; grid-template-columns: repeat(3,1fr); }
.loop-steps li { display: grid; grid-template-columns: 34px 1fr; gap: 10px; padding: 8px 20px; border-inline-start: 1px solid var(--line); }
.loop-steps li:first-child { border-inline-start: 0; }
.loop-num { color: var(--accent); font-family: var(--serif-display); font-size: 26px; font-weight: 900; line-height: 1.2; }
.loop-steps b { display: block; font-family: var(--serif-display); font-size: 20px; }
.loop-steps small { display: block; color: var(--ink-soft); font-family: var(--sans); font-size: 11px; line-height: 1.6; }

.catalog-head { display: grid; grid-template-columns: minmax(240px,.7fr) minmax(340px,1fr); gap: 60px; align-items: end; padding-top: 22px; border-top: 3px solid var(--ink); }
.catalog-head h2 { margin: 0; font-family: var(--serif-display); font-size: clamp(38px,5vw,56px); line-height: 1.1; }
.catalog-head p { margin: 10px 0 0; color: var(--ink-soft); font-family: var(--sans); font-size: 13px; }
.catalog-tools { display: grid; gap: 14px; }
.search-box { position: relative; display: grid; gap: 5px; color: var(--ink-soft); font-family: var(--sans); font-size: 11px; font-weight: 700; }
.search-box input { width: 100%; height: 52px; padding: 8px 18px 8px 50px; border: 1.5px solid var(--ink); border-radius: var(--radius); background: var(--card); color: var(--ink); font-family: var(--sans); font-size: 14px; }
.search-box input::placeholder { color: var(--ink-faint); }
.search-box kbd { position: absolute; inset-inline-end: 12px; inset-block-end: 11px; min-width: 28px; height: 28px; border: 1px solid var(--line); background: var(--paper); color: var(--ink-soft); font-family: var(--sans); text-align: center; line-height: 26px; }
.filters { display: flex; flex-wrap: wrap; gap: 4px; }
.filter, .clear-search { border: 0; border-bottom: 2px solid transparent; background: transparent; padding: 7px 12px; color: var(--ink-soft); font-family: var(--sans); font-size: 12px; font-weight: 700; cursor: pointer; }
.filter:hover, .filter.is-active { color: var(--ink); border-bottom-color: var(--accent); }

.phase-map { margin-top: 52px; scroll-margin-top: 22px; }
.cluster-heading { margin: 76px 0 10px; padding-bottom: 8px; border-bottom: 1px solid var(--line); color: var(--ink-soft); font-family: var(--sans); font-size: 11px; letter-spacing: .14em; }
.cluster-heading:first-child { margin-top: 0; }
.phase-row { border-bottom: 1px solid var(--line); scroll-margin-top: 18px; }
.phase-row.is-current { background: var(--accent-tint); }
.phase-toggle { width: 100%; min-height: 116px; padding: 18px 8px; border: 0; background: transparent; display: grid; grid-template-columns: 72px minmax(220px,1fr) 180px 120px 54px; gap: 22px; align-items: center; text-align: start; cursor: pointer; }
.phase-toggle:hover { background: var(--paper-2); }
.phase-number { font-family: var(--serif-display); font-size: 42px; font-weight: 900; line-height: 1; }
.is-current .phase-number { color: var(--accent); }
.is-future .phase-number { color: var(--ink-faint); }
.phase-titles b { display: block; font-family: var(--serif-display); font-size: 23px; line-height: 1.3; }
.phase-titles small { display: block; color: var(--ink-soft); font-family: var(--sans); font-size: 12px; }
.phase-measure { display: grid; grid-template-columns: 48px 1fr; align-items: center; gap: 12px; }
.phase-count { color: var(--ink-soft); font-family: var(--sans); font-size: 11px; text-align: end; }
.phase-track { height: 4px; overflow: hidden; background: var(--line); }
.phase-fill { display: block; height: 100%; background: var(--accent); }
.phase-status { color: var(--ink-soft); font-family: var(--sans); font-size: 11px; font-weight: 700; }
.is-current .phase-status { color: var(--accent); }
.phase-open { color: var(--accent); font-family: var(--sans); font-size: 11px; font-weight: 700; text-align: end; }
.phase-lessons { display: grid; grid-template-rows: 0fr; opacity: 0; transition: grid-template-rows .32s cubic-bezier(.2,.8,.2,1), opacity .22s ease; }
.phase-row.is-open .phase-lessons { grid-template-rows: 1fr; opacity: 1; }
.phase-lessons-inner { min-height: 0; overflow: hidden; display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); padding: 0 80px; }
.phase-row.is-open .phase-lessons-inner { padding-block: 10px 34px; }
.lesson-row { min-height: 74px; padding: 12px 14px; border-top: 1px solid var(--line); display: grid; grid-template-columns: 50px minmax(0,1fr) 66px; gap: 12px; align-items: center; color: var(--ink); text-decoration: none; }
.lesson-row:nth-child(2) { border-top-color: transparent; }
.lesson-row.is-built:hover { background: var(--card); }
.lesson-row.is-future { color: var(--ink-faint); }
.lesson-row.is-complete .lesson-row-action { color: var(--ok); }
.lesson-row.is-due .lesson-row-action { color: var(--terra); }
.lesson-row.is-due { background: color-mix(in srgb, var(--terra) 5%, transparent); }
.phase-row.learning-due { background: color-mix(in srgb, var(--terra) 5%, var(--card)); }
.phase-row.learning-mastered .phase-number,
.phase-row.learning-mastered .phase-status { color: var(--ok); }
.phase-row.learning-due .phase-number,
.phase-row.learning-due .phase-status { color: var(--terra); }
.lesson-row-number { color: var(--ink-faint); font-family: var(--sans); font-size: 10px; letter-spacing: .06em; }
.lesson-row-titles { min-width: 0; }
.lesson-row-titles b { display: block; overflow: hidden; text-overflow: ellipsis; font-family: var(--serif-text); font-size: 15px; line-height: 1.35; white-space: nowrap; }
.lesson-row-titles small { display: block; overflow: hidden; color: var(--ink-soft); font-family: var(--sans); font-size: 10px; text-overflow: ellipsis; white-space: nowrap; }
.lesson-row-action { color: var(--accent); font-family: var(--sans); font-size: 10px; font-weight: 700; text-align: end; }
.is-future .lesson-row-action { color: var(--ink-faint); }

.search-results { margin-top: 44px; padding: 24px 28px; border-block: 1px solid var(--ink); background: var(--card); }
.results-head { display: flex; justify-content: space-between; align-items: center; gap: 20px; margin-bottom: 8px; }
.results-head h3 { margin: 0; font-family: var(--serif-display); font-size: 26px; }
.clear-search { color: var(--accent); }
.search-results .lesson-row { grid-template-columns: 58px minmax(0,1fr) 80px; }
.results-limit, .empty-filter { padding: 24px; color: var(--ink-soft); font-family: var(--sans); font-size: 13px; text-align: center; }

.hub-footer { margin-top: 110px; padding-top: 26px; border-top: 3px solid var(--ink); display: flex; justify-content: space-between; gap: 20px; color: var(--ink-soft); font-family: var(--sans); font-size: 12px; }
.hub-footer a { color: var(--accent); text-decoration: none; border-bottom: 1px solid var(--accent-line); }

@media (max-width: 900px) {
  .today, .study-loop, .catalog-head { grid-template-columns: 1fr; }
  .availability { border-inline-start: 0; border-top: 1px solid var(--line); }
  .study-loop { gap: 26px; }
  .catalog-head { gap: 30px; }
  .phase-toggle { grid-template-columns: 58px minmax(160px,1fr) 130px 90px 46px; gap: 12px; }
  .phase-lessons-inner { padding-inline: 28px; }
}

@media (max-width: 640px) {
  body { font-size: 16px; }
  .hub-masthead { min-height: 62px; padding: 16px 20px; }
  .hub-brand-en { display: none; }
  .hub-nav { gap: 10px; font-size: 10px; }
  .hub-wrap { padding-inline: 18px; }
  .hub-hero { padding-block: 54px 44px; }
  .hub-hero h1 { font-size: clamp(43px,14vw,64px); }
  .today-main, .availability { padding: 26px 20px; }
  .study-loop { margin-block: 54px 76px; }
  .loop-steps { grid-template-columns: 1fr; }
  .loop-steps li { border-inline-start: 0; border-top: 1px solid var(--line); padding: 14px 0; }
  .loop-steps li:first-child { border-top: 0; }
  .phase-map { margin-top: 34px; }
  .cluster-heading { margin-top: 54px; }
  .phase-toggle { min-height: 104px; grid-template-columns: 46px minmax(0,1fr) 34px; gap: 10px; }
  .phase-number { font-size: 34px; }
  .phase-titles b { font-size: 19px; }
  .phase-measure, .phase-status { display: none; }
  .phase-lessons-inner { grid-template-columns: 1fr; padding-inline: 8px; }
  .lesson-row:nth-child(2) { border-top-color: var(--line); }
  .lesson-row { grid-template-columns: 42px minmax(0,1fr) 50px; padding-inline: 4px; }
  .search-results { padding: 18px 12px; }
  .hub-footer { flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .phase-lessons, .primary-action, .secondary-action { transition: none; }
}